By Erika Edwards -
NBC News
A combination of several common viruses could be behind the mysterious outbreak of cases of children with severe liver damage that began to manifest in late 2021, as COVID-19 restrictions began to be lifted and schools reopened.
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Serious cases of hepatitis and liver failure are extremely rare in children.
healthy and concerned experts.
In the United States, the Centers for Disease Control and Prevention has investigated 390 cases in 46 states as of fall 2021. A total of
22 children required liver transplants and 13 died.
Worldwide, there have been 1,000 cases, according to the World Health Organization.
Serious cases of hepatitis and liver failure are extremely rare in otherwise healthy children and have worried experts.Getty Images
Research published Thursday in the journal Nature focuses on a possible culprit: adeno-associated virus 2, or AAV2, a virus not known to cause disease.
In 93% of the cases, the investigators detected AAV2.
Three or four viruses at once
More important, the researchers found that AAV2 did not appear to be acting alone.
It needed other viruses to help it enter cells.
The study focused on 16 children in the United States with severe hepatitis, who had blood and stool samples taken and liver biopsies performed.
In most cases, the patients were infected with three or four common viruses at the same time.
Multiple infections "was an expected outcome," said Dr. Charles Chiu, the study's lead author and director of the Clinical Microbiology Laboratory at the University of California-San Francisco.
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In 75% of the cases, the researchers found evidence of infections with at least three viruses at the same time.
In a third of the cases, there was evidence of four viruses.
The researchers detected several viruses.
One of them was adenovirus type 41, which had previously been identified as a potential culprit for the disease.
That virus usually causes stomach upset.
The researchers also found the herpes virus, an enterovirus, and the Epstein-Barr virus, which can cause mononucleosis.
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The results do not prove that these infections were the direct cause of severe hepatitis, but they did offer important clues.
The findings were compared with 113 pediatric patients who were either healthy or had liver problems for which the cause was known.
There was no evidence of multiple viruses in that group.
Two studies published last summer also detected AAV2 in minor patients with severe hepatitis in the UK.
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"Similar results from three independent studies give the findings great credibility," Thomas Baumert, head of the Inserm Research Institute for Viruses and Liver Diseases at Strasbourg University in France, said in a statement.
Baumert was not part of the investigation.
It's not uncommon to see children with several viruses at the same time, usually without a tragic end, said Dr. Ibukun Kau, a specialist in children's infectious diseases at Duke University Hospital in North Carolina.
"You can have a baby sneezing for a month, even when we expect a viral infection to last about two weeks."
What worries
Kalu, however, is the possibility that "historically non-pathogenic viruses are becoming pathogenic when combined with or present with other viruses."
The aggravating circumstance of COVID-19
There is no indication that COVID-19 or vaccines against it are related to these cases.
But the cases are likely a consequence of the pandemic, Chiu said.
When the schools were closed, the children were not exposed to the common viruses that usually circulate.
When the restrictions were lifted, children were suddenly exposed to multiple viruses at the same time.
Photos taken by a microscope of the hepatitis A virus.Getty Images
Globally, cases have been in young children, 10 years of age or younger.
"This is precisely the period of time when the immune system is being formed," Chiu explained.
"What I suspect happened is that this segment of the population of children had impaired immune system development for more than two years."
"One of the unintended consequences of the COVID-19 pandemic may have been that we now have a population of children who have modified immune systems," Chiu said.
"We have to be alert to the possibility that we could be seeing unusual manifestations of diseases like hepatitis in the future."
"One of the unintended consequences of the pandemic may be that we now have a population of children with modified immune systems."
dr.
study author charles chiu
Although cases linked to the recent outbreak appear to be on the decline, Dr. Any Feldman, medical director of pediatric transplants at Children's Hospital Colorado in Colorado Springs, said she sees a number of unexplained cases of liver failure each year.
His team has added adenovirus screening for his pediatric patients with liver inflammation.
Understanding the potential causes of these cases can help doctors "better understand how to prevent and treat them," he explained.
"Stopping the spread of germs is important," she said, and "the more you wash your hands, the better."
